Exemplary embodiments of the present invention relate to a motor vehicle having a driver assistance unit and a method to operate a driver assistance unit.
Known methods for operating driver assistance units employ suitable detection units to detect environmental parameters that contain information about the surrounding environment of the motor vehicle. Thus, for example, obstacles in a road can be detected. To avoid a collision, the detected environmental parameters are compared with current driving parameters, such as, for example, a yaw angle of the motor vehicle and/or a motor vehicle speed, in order to assess the risk of collision. If a risk of collision exists for the motor vehicle, then a deceleration of the motor vehicle is autonomously triggered by the driver assistance unit, in order to avoid a crash of the motor vehicle or at least to decrease the severity of the crash.
German patent document DE 10 2009 020 649 A1 discloses a method and device to avoid collision for a motor vehicle in which deviation trajectories are calculated in the case of a threatening collision, which are applied to interval limits. When the interval limits are achieved, a warning is displayed for the driver and a deviation maneuver is initiated.
Furthermore German patent document DE 101 02 772 A1 discloses a device and a method for adaptive driving speed regulation of a motor vehicle in which automatic steering interventions and/or braking can be carried out depending on a recognized dangerous situation, in order to reduce the risk of collisions of the motor vehicle.
Exemplary embodiments of the present invention are directed to an improved motor vehicle having a driver assistance unit and an improved method for the operation of a driver assistance unit.
A motor vehicle has a driver assistance unit, which comprises at least one detection unit to detect an environmental parameter and a brake unit. The driver assistance unit is formed in such a way that an autonomous deceleration of the motor vehicle is able to be carried out in the case of risk of collision, recognized by means of the environmental parameter. According to the invention, the driver assistance unit is formed in such a way that an autonomous emergency stop is only then able to be carried out if the motor vehicle has at least one reversible seat belt pre-tensioner.
The driver assistance system is able to brake the motor vehicle autonomously. An autonomously initiated deceleration can, however, catch a vehicle driver or a vehicle passenger unprepared and be initiated at an inappropriate moment, in which a sitting position of the vehicle driver or of the vehicle passenger is not optimally adjusted to a collision situation. Moreover, an upper body of the vehicle driver or of the vehicle passenger is typically shifted forwards during the braking process due to the inertia, before this forward movement can be stopped by a seat belt. Through the upper body being shifted forwards during the autonomously initiated deceleration, however, an increased risk of injury for the vehicle passenger or vehicle driver results in the case of collision, as the upper body protrudes into a region of an inflatable air bag. Injuries through the inflation of the air bag cannot occur. Additionally, through the forward inclination of the upper body, an increased load, in particular in the throat and neck region, results if the upper body of the vehicle driver or the vehicle passenger collides with the inflated air bag. In order to reduce this increased risk of injury, the maximum deceleration of the motor vehicle is limited to a maximum amount in the case of the autonomously initiated deceleration. The driver assistance unit is constructed such that an emergency stop of the motor vehicle, in the case of which a deceleration force acting on the motor vehicle is limited by the design of the braking unit of the motor vehicle, is only then possible if the motor vehicle has a reversible seat belt pre-tensioner. Therein the reversible seat belt pre-tensioner is controllable in such a way that the sitting position of the vehicle driver and/or the vehicle passenger can already be fixed before the initiation of the autonomous deceleration by means of the safety belt being tightened, such that the risk of injury in the case of an accident of the motor vehicle is reduced.
In a method to operate a driver assistance unit for a motor vehicle, a risk of collision is recognized by means of at least one detected environmental parameter. In the case of a recognized risk of collision, an autonomous deceleration of the motor vehicle is triggered. According to the invention, depending on the autonomous deceleration to be triggered, an activity of a drive unit of a reversible seat belt pre-tensioner is examined. The autonomous deceleration of the motor vehicle is limited to a maximum amount, which lies below a maximum magnitude of the deceleration of the motor vehicle by design, if the examination of the activity of the passenger protection unit gives a negative result. If the examination of the drive unit of the seat belt pre-tensioner gives a positive result, then the maximum deceleration of the motor vehicle is not limited and an autonomous emergency stop of the motor vehicle is initiated in the case of actual dangerous conditions.
The limiting of the deceleration of the motor vehicle, initiated autonomously by the driver assistance unit, to a maximum amount should reduce an undesired and potentially dangerous forward inclination of a vehicle passenger due to mass inertia. Therein, in particular, the posture of the vehicle passenger is decisive at the time of the collision, in which an air bag of the passenger protection unit is triggered and inflated. If, at the time of the collision, the upper body of the vehicle passenger is inclined too far forwards, there exists an increased risk of injury for the vehicle passenger during the inflation of the air bag. In particular, in the case of forward inclination, a neck region of the vehicle passenger is exposed to an increased load, which does not occur, if, fundamentally, the body of the vehicle passenger is fixed in a regular sitting position at the time of the collision.
In the case of a recognized risk of collision, a deceleration of the motor vehicle is autonomously initiated. If the amount of the initiated deceleration, so the amount of a negative accelerating force which is to act on a motor vehicle, exceeds the predetermined maximum amount, then it is queried whether a passenger protection unit, suited to fixing the sitting position is activated and/or functional. In particular, the passenger protection unit can comprise a reversible seat belt pre-tensioner. If the passenger protection unit is activated and functional, then the restriction of the autonomous deceleration to the maximum amount is overridden, as it can be assumed that the vehicle passenger is fixed in a secure sitting position. Thus, an autonomous emergency stop can be initiated, in the case of which the accelerating forces acting on the motor vehicle are only limited by the design. If the passenger protection unit is not functional or is deactivated, then the examination of the same gives a negative result. Correspondingly, the autonomously initiated deceleration of the motor vehicle is limited to an amount below the maximum amount, in order to avoid a higher risk of injury of the vehicle passenger.